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Abstract

In this paper, we present a numerical and experimental study of W3-4 photonic crystal (PhC) waveguide lasers fabricated on InP substrate. In such a PhC waveguide, the dispersion curve of the fundamental mode folds in the two-dimensional gap of the triangular lattice. Folding occurs at the Brillouin zone edge as in the case of genuine distributed feedback (DFB) lasers. Single-mode emission is presently observed in both electrical and optical pumping configurations. This behavior is attributed to the different levels of out-of-plane losses experienced by the two DFB mode components. Three-dimensional finite-difference-time-domain calculations are used to finely quantify the quality factors of the waveguide modes. The modal discrimination is shown to be reinforced when lasing occurs far from the conduction band edge. This trend is also predicted for other canonical waveguides in triangular PhCs as for instance W2-3 waveguides.

Figures (5)

Left: band diagram of the W3-4 waveguide in TE polarization calculated from a 2D
plane wave model with the supercell method. The thick curve is for the fundamental mode.
Right: H field patterns of the modes at normalized wave vector k=0.5 and normalized
frequencies a/λ=0.2725 and 0.273, respectively.

Left: dispersion curves of the odd modes with the longest lifetime τ represented near the Brillouin zone edge around the normalized frequency a/λ=0.27. Calculations are performed with the 3D FDTD model. Right: Quality factor Q=τω of the modes versus the normalized frequency. Inset: Schematic view of the simulated W3-4 waveguide with the active layer in dark gray.

Left : Evolutions of the TE gap (white area) and of the normalized DFB laser
frequencies at k=0.5 (solid lines) versus the hole radius in normalized units r/a. Right: Evolutions of the Q-factors of the high and low frequency modes at k=0.5 with the hole radius (3D FDTD simulations).